1. Technical Field
The present invention relates to an inertial sensor.
2. Description of the Related Art
Recently, MEMS (Micro-Electro-Mechanical Systems) technology has made it easy to manufacture small and light inertial sensors. This extends the range of application of inertial sensors to electric home appliances beyond the existing market. The functions of the inertial sensors are also continuously developing from single-axis sensors in which a single sensor can detect an inertial force with respect to a single axis, to multi-axis sensors in which a single sensor can detect inertial forces with respect to two or more multiple axes.
Piezoelectric elements are devices which are used to embody the inertial sensors and change in shape when a voltage is applied thereto and, conversely, generate a voltage when deformed. Due to these characteristics, the piezoelectric elements are widely used in a variety of actuators, sensors, etc. Further, there are different kinds of materials, for example, Aln, ZnO, quartz, etc., which can be used as the material of such a piezoelectric element. Particularly, PZT (Lead Zirconate Titanate) is widely used in a variety of fields, because its piezoelectric constant is comparatively large.
Methods of embodying inexpensive very small inertial sensors are mainly classified into a capacitive type and a piezoelectric type. Compared to the capacitive type, the piezoelectric type is advantageous in that normal pressure packaging is possible without making use of vacuum packaging.
Such an inertial sensor requires precise and effective time-sharing drive and control to embody it as a multi-axis inertial sensor, that is, a six-axis sensor that is associated with three-axis acceleration and three-axis angular velocity. In the case of an inertial sensor according to the conventional technique, sensing three-axis angular velocity using a single driving mass includes successively conducting X/Y-axial drive and Z-axial drive in a time-sharing manner, and successively sensing Z-axial angular velocity and X/Y-axial angular velocity.
As such, the piezoelectric type of inertial sensor embodies the driving and sensing at the same time so that it is possible to sense a static signal. However, it is impossible to sense a DC signal, that is, associated with the direction of gravity.